1. Technical Field of the Invention
The present invention relates to the field of integrated circuit packaging, and more particularly to the packaging of three-dimensional memory (3D-M).
2. Prior Arts
A three-dimensional memory (3D-M) chip comprises a plurality of vertically stacked memory levels. By using 3D-stacking, 3D-M has an increased storage capacity. However, because 3D-stacking is a very demanding manufacturing process, only three-dimensional one-time-programmable memory (3D-OTP) and three-dimensional mask-programmable memory (3D-mM) can be mass-produced in the foreseeable future. For these 3D-M's, their contents are generally recorded before customer delivery. Accordingly, they are primarily used as pre-recorded memory. As a pre-recorded memory, 3D-M is expected to store a large amount of multimedia contents, particularly a movie library.
U.S. Pat. Nos. 5,835,396, 6,034,882, 6,385,074 and others disclose various types of 3D-M. FIG. 1A illustrates a typical 3D-M, i.e. 3D-OTP 10 (referring to Moore, “Matrix Semiconductor White Paper, Matrix 3-D Memory Roadmap Advancements”, May 2005; and U.S. Pat. No. 5,835,396). It comprises four memory levels 10a-10d. Each memory level comprises a plurality of word lines (e.g. 12), bit lines (e.g. 14) and memory cells (e.g. 18). Each memory cell 18 further comprises a diode (not shown in the figure) and an antifuse 16. The antifuse 16 comprises a layer of insulating dielectric, which breaks down during programming. This leads to a high resistance before programming and low resistance after programming. Inter-level dielectric 13 provides electrical separation between memory levels (e.g. 10c, 10d). Memory-level vias (also known as interlevel connecting vias in the '396 patent) (e.g. 10av) provide electrical connection between memory levels (e.g. 10a) and the substrate 11. At present, industry generally believes that, among all 3D-M's, 3D-OTP has the greatest commercial potential; and the majority research and development efforts are devoted into this area.
Before shipping, a 3D-M chip needs to be packaged into a 3D-M module. U.S. Pat. No. 6,545,891 discloses such a 3D-M module 20. As illustrated in FIG. 1B, it is housed in a standard memory package (e.g. CompactFlash card or SecureDigital card), which can be easily inserted into or pulled out from a mobile device. This 3D-M module 20 comprises a single 3D-M chip 26 and an interface chip 28, which are placed side-by-side on a substrate 24. Its 3D-M chip 26 is a 3D-OTP (see FIG. 9 of the '891 patent); and its interface chip 28 converts the 3D-M data into a standard format (e.g. CompactFlash format or SecureDigital format), but does not limit access to the 3D-M data.
U.S. Pat. No. 6,731,011 discloses another 3D-M module 30. As illustrated in FIG. 1C, it also comprises a 3D-M chip 36 and an interface chip 38, which are vertically stacked on a substrate 34. Similar to FIG. 1B, its 3D-M chip 36 is preferably a 3D-OTP (see FIG. 6 of the '011 patent); and its interface chip 38 does not limit access to the 3D-M data.
The prior-art 3D-M module (20 or 30) prefers 3D-OTP (26 or 36) as its 3D-M chip. However, among all 3D-M's, 3D-OTP has neither the largest storage capacity, nor the lowest storage cost. In fact, 3D-mM excels 3D-OTP in both aspects (referring to FIG. 5/Table 1). Adding the fact that it typically just comprises a single 3D-M chip, the prior-art 3D-M module has a limited growth potential in storage capacity.
Besides having a limited storage capacity, the prior-art 3D-M module (20 or 30) faces a more serious hurdle—its pricing model is hard to accept for most consumers. Because the interface chip of the prior-art 3D-M module does not limit access to its contents, a customer can access any of its contents upon obtaining it. This means all copyright fees must be paid upfront during purchase. Accordingly, the initial selling price (ISP) of the prior-art 3D-M module should include not only its hardware cost, but also the copyright fees of all contents. As more and more contents are stored in a 3D-M module, the pre-recorded memory based on the prior-art 3D-M module will have a very high ISP, and this will lead to a high market entry barrier. For example, by using the storage-enhancing means disclosed in the present invention, a 3D-M module can store ˜64 GB, or ˜120 movies, which require an ISP of ˜$1,000, a number too high for most consumers. In addition, charging all copyright fees upfront is not fair, because consumers may not want to access all contents in a 3D-M module and do not wish to pay for the contents they are not interest in.
In order to overcome these drawbacks, the present invention discloses a three-dimensional-memory-based three-dimensional memory module (3D2-M2) and system thereof. 3D2-M2 is an ultra-low-cost, ultra-large-capacity and small-form-factor memory module, whose pricing model is more acceptable to consumers.